Near death experiences (NDEs) have been reported throughout world in essentially all cultures, including amongst the believers of the Hindu religion The contents of NDEs are independent of the gender, age, profession, religion, belief of soul, belief in angels of death or ghosts and belief in death kingdom and heaven, of people who experienced it. The frequency of occurrence is estimated to be between 5% to 48% in adults, and around 85% in children who experienced near-death situations. This frequency may be higher still, perhaps even 100 percent, were it not for the dreamlike and dissociative character of these experiences, and the amnesia-prone participation of the temporal lobe cortex of brain, causing a clear tendency to forget the NDE. A number of experiences can be very similar to NDEs, such as review of one's life in this planet, or an out-of-body experience (OBE,) in which the physical body and its surroundings are observed from various external vantage points, often from above, such that the body is passing through a deep dark tunnel, or seeing flash of light equal to thousands of sun for pure souls. The experience of seeing God and conversing with him, seeing alien lands, seeing dead relatives or someone's future, can all be regarded as similar in nature. Many individuals have reported horror experiences as well. Numerous cases-are existing in which the reality of the the OBE-observation can be independently 'verified, by external conditions, situations, people, objects, etc. Even people who are non-religious, subsequent to NDE experiences have displayed a markedly decreased fear of death, and a corresponding increase in the belief in "life after death" and re-incarnation. Certain elements of NDE- experiences can be induced by drugs, such as hallucinogenic substances and anesthetic drugs like ketamine, and electrical stimulation of the right temporal lobe or the limbic system has also produced such effects. The possibility that the hallucinogenic transmitters (and endorphins) of the brain themselves play a role in the NDE has been postulated. Nevertheless, there are NDE-elements, such as the frequently reported quick life-reviews, and the acquisition of external, verifiable information about the physical surroundings, that cannot be explained. Wish-fulfillment, death-denial or fighting against death, and other defense mechanisms of the brain, are also not adequate explanations. The large body of NDE data now points to genuine evidence for a non-physical reality. The paranormal capacities of the human being also raises the question: Does the human soul exist?

Keywords: Near death experiences, human consciousness, quantum theory, near death experiences stages, scientific theory of near death experiences

How to cite this article:
Bhattacharya PK. Is there science behind the near-death experience: Does human consciousness survives after death?. Ann Trop Med Public Health 2013;6:151-65

From times immemorial, humans have been curious to know about what happens during the time of death. Also, questions such as does the soul exist, and if it does, where does it land up after death, have been raised. Also, it has been asked if a human's soul and an animal's soul all land up in the same place after death, or are they treated differently. Is there any re- incarnation? In my article, I have tried to talk about Near Death Experiences (NDE) of people and and probable re-incarnation.

A near-death experience (NDE) refers to a broad range of experiences of people associated with impending death; however, somehow the persons managed to revive back to life. It has been variously described till today, including sensations of detachment from the body; floating in space- time and seeing his/her corpus, feelings of levitation; extreme fear of dying; total serenity, often or sometimes security, or warmth; experience of absolute dissolution; and presence of a bright light, ending up in an alien lands or meeting with people or relatives who have already died. [1],[2] Such cases are usually reported after an individual has been pronounced clinically dead, or otherwise very close to death, and hence the name "near-death" experience. However, we need to note that many NDE reports, have originated from events which are not even life threatening. With advancements in medical science and developments in cardiac resuscitation (CPR) techniques, the number of NDE cases reported worlwide has increased significantly.

Most of the scientific community regards such experiences as plain hallucinations, while many paranormal specialists and some mainstream scientists and aesthetics claim these to be evidences for "an after-life" or "existence of soul". Professor Siben Saha MD (Med), Ex- Professor and Head of Department Tropical Medicine, Calcutta school of tropical medicine (CSTM) and I have previously written about our work on NDE, and presented it on the Foundation Day Souvenir of Kolkata School of Tropical Medicine on February 24 th 1997.[2] I have much interest in the human consciousness, and often ask myself- What is actually the human consciousness? How does it enter the human fetus at 28 weeks of gestation? It is the driving force of all human beings? Or is it just simply the human rain, or heart or lung? What happens to it and where does it go when a human dies? I believe that without consciousness, a human being can be compared to a lump of organ specific cells, made of matter and organic compounds such as Carbon, Hydrogen, Nitrogen, Phosphorus, Sulfur, and Oxygen, which make up the Deoxyribonucleic acid (DNA) proteins, cell membranes and cell nuclei. Is a single cell, such as a brain neuron, say astrocyte, or a simple organism such as protozoa aware of its existence? Can we not draw inspiration of the very intricate functions a single cell performs - which even a super computer or a robot cannot achieve with that precision and perfection? What is the very meaning of "I" or the existence of "I am"? Is there any eternal connection between the human consciousness and space, time, quantum particles and physics?

Renowned theoretical physicist Roger Penrose FRS (London), once concluded that the physiological process underlying a given thought process initially involve numbers of superposed quantum particle states, each of which performs a calculation of sorts like a computer or a super computer. Thus, is the human mind much unlike a computer? Penrose thinks the answer might have something to do with quantum physics! Any system at the quantum particle level (a group of hydrogen atoms, for instance) should not have a single course of behavior, r a single state, but a number of different possible states that are somehow "superposed" on one another. I would here want to highlight the same point that was given by Sir Andrie shakarov - The Russian Nobel Peace Laureate and Solid State Physicist in his CP violation theories, that at the quantum particle level, a quark particle may have two or more constantly changing positions. When a physicist measures a system, all the superposed states collapse into a single state and only one state and possibility remains. There are also terms such as "Quantum Gravity" and "quasi crystals". Ordinary crystals grow serially, one atom at a time; however, the complexity of quasi crystals suggests a more global phenomenon: each atom seems to sense what a number of other similar atoms are doing as they fall into place in a concert, what I do think. This process reminds me of the "Tiles theorem" by Rogers Penrose; the proper placement of one tile often depends on the positioning of other tiles. Similarly, we can describe the human mind and consciousness. Their growth depends upon the proper placement with other minds in the society. However, is all this related to the Human Consciousness? According Rogers Penrose, the quantum process cannot be replicated by any super computer or robot till today. Are human minds subject to the laws of "Quantum physics"? Roger Penrose's Book "The Emperor's New Mind Human Intelligence" outstrips artificial intelligence that exploits physics at the quantum-mechanical level. Look at Schrödinger's [the NL in Physics] famous cat experiment. In this thought experiment, a scientist who has no fear of animal and light activists, places a cat and a vial of toxic gas in a room that contains a laser, a half-silvered mirror, a light detector and a hammer. When the room is sealed, the laser emits a photon toward the mirror. If the photon passes through the mirror, no harm comes to the cat. But if the photon is reflected in the mirror, it hits the detector, which activates the hammer, which smashes the vial, which contains the poisonous gas, which kills the cat. From outside the room, one cannot know whether the cat lives or dies. In the quantum-mechanical worlds, so the two possible events coexist as superimposed realities. However, in the classical world, only any one event may occur.

In Quantum systems, the famous two-slit experiment says the possibility that a photon particle can be in two places at a one co-ordinated time. Even for Penrose, human consciousness has a non-algorithmic ingredient. At the quantum level, different alternatives can coexist at single time or co-ordinates. A single quantum state could in principle consist of a large number of different, simultaneous activities. Is human brain somehow able to exploit this phenomenon? When the differences in the distribution of mass and energy between the states reach at a gravitationally significant level, the different states collapses into a single state, causing measurable and possibly non-local changes in the neural structures of human brain cortex, that is, the sulci and gyri. The physical events correlate with a mental image: Consciousness can exit outside the body. I would like to put this forward as the human brain being in another state. Let me think about the comprehension of a mathematical theorem, or the decision not to tip a waiter. Let's come back to the human mind. For Roger Penrose, consciousness is a non-algorithmic ingredient. At quantum particles and sub-particles level, different alternatives should co-exist. A single quantum state can in principle consist of a large numbers of different, simultaneous activities. Is the human brain somehow able to exploit this phenomenon? I am inspired with such concepts, and wish to understand the questions related to this. Can human beings quantify their own intelligence in a universe, which has a mostly homogeneous (Isotropic), slight and non-homogeneous (Freidman's universe model) structure?

The universe is regarded as anisotropic, expanding forever, having 22 dimensions (at least ten dimensions per String Theory III or in M theory Model and our De- quatrain universe of Einstein; or four dimensions in the Brane Model of Universe) Strings theories are today the most acceptable theories of structure and origin of the universe. Cosmic strings are predicted by many field-theory models, and probably were formed at a symmetry-breaking transition phase in the early history of the universe or at some moment of Planck point, such as that associated with grand unification. They could have important cosmological effects. Scenarios suggested by fundamental string theory or M-theory, in particular the popular idea of brane inflation, also strongly suggest the appearance of similar structures. However, cosmic strings are very thin (with widths of order 1/ms =1/(√lh) or 1/mv = 1/(eh)). Their large-scale dynamics in an otherwise empty or low-density universe was very well described by the Nambu-Goto action(Nobel prize in physics), by explaining the zero-width approximation. The space time coordinates of points on the string are xm(sa), where sa (a = 0, 1) are two world-sheet coordinates, and the action is required to be invariant under arbitrary re parametrizations sa → sa . In fact, the Nambu-Goto action is simply proportional to the area of the world-sheet: String theory is based on the idea that the fundamental constituents of matter are not point particles but tiny strings, either open or closed (forming loops; for an introduction, see Polchinski 1998; Becker et al, 2007). The theory can only be made consistent in a space time of more than the familiar four dimensions-26 for bosonic strings or 10 for superstrings.

General theory of relativity based on four dimension (taking Time as a dimension and any events as coordinate), and three arrows of time where future cannot be felt have been proposed. If the consciousness is made of the most finest subatomic elementary particles, then can it follow Schrφdinger's Cat box experiment? There are in fact multiple universes like/ or unlike our observable universe based on subatomic particles and anti- Particles [Rupak Bhattacharya and Prof. Pranab Kr Bhattacharya's Multiple electrical universe Model Theory]. An end to any structure of our observable matter (hadron), or human body and it's organs or any living things, or nonliving things such as ultimate particles of six types of quarks, or a set of sub2 quarks particles, seems conceivable. This is applicable not just for particles, but any damn structure, whether energy, Gravity (Graviton) or even purely information, or if there is, even the soul. All these may be made of sub2 atomic, invisible particles to the human eye and the highest power microscope; however, may be detectable at Large Hadron Collider (LHC) on Proton and Proton collider at European Organization for Nuclear Research (CERN)- Geneva. What about the Higgs particles? It seems to me that quantum level physics at Quantum Chromo dynamics levels (QCD) itself, may be an infinite enterprise for sample reasons that as soon as some 'ultimate' structure is discovered, explaining existence of the 'ultimate laws" of our observable universe, becomes the next problem. In any event, I shall prefer to live in a structured universe which is infinitely open, and expanding and contracting alike. For one thing, our minds are more powerful than any other structures. Computers and supercomputers, super conductors, artificial intelligence, and robots constructed with humanitarian feelings and senses, and with the capability to understand the human languages and feelings, help us to rule out the influence of any other special physical process below the size of quantum particles and sub-particles.

As the next step, Deoxyribonucleic acid (DNA) robots have been created to cure human cancer. They can isolate cancer cells from normal cells and can destroy them by delivering drugs or correcting mutations. The algorithm must be protected from errors." Our human brains may or may not be as structured", as Rogers Penrose pointed out very rightly. Physical events at the sub atomic particle level may be playing an important role in the human thought process formation and consciousness. There are processes in the brain which operate at the chemical molecular levels. One can think about the influences of all neuron-transmitter molecules on the behavior of neurons in the brain, such as endorphins. Furthermore, it is a well-known characteristic of nature to take advantages of physical possibilities in the deployment of biological operations. If physical structures can be extended to a certain level, is there any reason to believe that the brain must automatically be excluded from exploiting it? What if the brain could exploit levels of structures in an infinitely structured universe? All these are rather questions to be asked for higher level quantum physics and mathematics and challenge the Big Bang theory. Artificial consciousness and intelligence today is possible through Super computer and semiconductors. NDEs also support Einstein's theory of time travel. Albert Einstein's theory of Special relativity allows for the possibility of time travel at the speed of light.

During a NDE, some people have however reported travelling back in time (quick past life review), and some have reported travelling into the future. But in real world, humans cannot see the future as there are three arrows of time. Does NDE support a theory of consciousness? Scientific knowledge is today also in a state of flux. New scientific discoveries come along and overthrow the long-held old hypotheses in human physiology, Medicine or Physics. A good example is the attempt by scientists to prove the phenomenon of light, E = Mc 2 , as a wrong equation Today it is called as wrong theory(!), as particles called as "Neutrinos" which travel faster than the speed of light have been discovered. Even the "Tachyons" particles travel faster than the speed of Light. [42] All the laws and theories of Physics will change if E = Mc 2 is proved wrong by the analysis of data obtained from the LHC at CERN.

Ancient religious texts around the world have associated light with divine consciousness, from which everything, including all other consciousness, originated. Before the dawn of science, humanity relied on religious experiences and philosophy to understand light and cosmos. Isaac Newton then theorized that light is composed of particles. Albert Einstein described the particle as "Photon" and having the highest speed in the Universe. Further scientific discovery overthrew their theories and led to the theory of light as "wave". After the discovery of the photoelectric effect, the wave theory was overthrown, and the "quantum" theory of light emerged, which described light as a near zero mass particle and a wave, both. Another theory of light proposed recently though not popularized well is the "Cone Theory" -It is based on the concept of space Time. Light moves from a coordinate in a cone shaped fashion called the Future cone and the present cone. Interestingly enough, this theory corresponds with a current mathematical theory of chaos, (one of theories to explain the origin of the Universe) which explains how human consciousness might be both, a part of the whole, and the entire whole of a single non-localized consciousness. Death is considered as chaos and anisotropy or "not in order" state. According to me, even Ventricular or atrial flutters or fibrillation may be considered as a type of chaos.

Science has yielded some very unusual discoveries about light. The energy of light is infinite as per E=Mc 2 . Light was pervasive at beginning of the universe as a photon particle. All other matter may be considered as have orginated from light (electromagnetic radiation). Time stops when on travels at the speed of light. This means that if you could travel at the speed of light, you could travel anywhere in the universe and could live forever as you are then nothing but simple energy (According to Einstein's Twin Paradox, there are two twins, and one of them is travelling at speed of light and he never ages, and when he returns back to earth after a year long travel in space time, he finds his other twin aged 80 years or more than what he was when the former first left earth). The speed of light is constant for all observers regardless of their relative speed or directions. Thus, time stops at speed of Light. Can light particles communicate with each other? Human observation transforms light waves into light particles to experience the reality. Humanity's scientific discovery of the nature of light is the cornerstone of modern physics and the natural laws of Universe. Will it also be the cornerstone of NDE research and consciousness research in the future?

Most NDE studies have described people having experiences with a beautiful and loving light equal to a thousand suns, while they were clinically dead. [24] People often describe this light in same way that ancient religious texts described it as divine consciousness. This demonstrates how scientists have scaled the mountain of ignorance to overcome the dangerous pitfalls of confusion, and conquered the steep summit of darkness to finally reach the peak of enlightenment, only to find what a group of holy men had been saying since a thousand years. Thus, humanity's struggle to ascertain the nature of light and consciousness remains elusive. The more one tries to concentrate on the location and source of light and consciousness, the more difficult they are to ascertain it.

The old paradigm of reliance on scientific methods, appears to be unable to conquer these challenges, because it assumes that nothing is true unless it can be quantified by human senses using scientific method. And if consciousness does not have either physical essence, or locality, then this paradigm may never be able to quantify it. It is here that we require the Quantum theory. In quantum and particles physics, Quarks, various sub particles - colours, gluons, neutrinos, Z paricles, W particles, leptons and fermions cannot be quantified, neither can be they be appreciated by the naked eyes or by microscopes. Similarly we have the Higgs particles. Many kinds of Higgs particles' that provided mass are probably existing. However, no one has ever found or seen them. But at the same time, the reality that they exist cannot be ignored. The search is on-going. A search for Higgs particles in the four-lepton decay channel H to ZZ experiment, with each Z boson decaying to an electron or muon pair, has been mathematically reported. The search hypothesizes the mass of the Higgs particles to be in the range of 110 < mH < 600 GeV.

The existence of the Higgs boson has yet to be established experimentally, while its mass, mH, is not fixed by the theory. The inclusive Higgs boson production followed by the decay of H to ZZ is expected to be one of the main discoveries by the CERN's proton-proton (pp) Large Hadron Collider (LHC) and will help to determine a wide range of mH values. Using the H to ZZ and the H to WW decay channels, the Atlas More Details collaboration have excluded at 95% confidence level (CL) the mass ranges of 45-206 GeV, 214-224 GeV, and 340-450 GeV. Thankfully, the quantum theory is allowing new paradigms to take flight, such as the theory that if the basic building blocks of universe are hadrons (matter), which are the finest, subatomic totally zero mass particles in GEV, or Rupak particles (R particles), or the Higgs fields, then why can't it be the consciousness itself?. What is Dark energy consisting of? No particles constituting dark energy have ever been found! However, in reality, it is believed to constitute 75% mass of our universe. Matter is regarded only 5% and the rest is regarded as "Dark matter". What is that? The scientists say it may be the weakly interacting massive particles (WIMPs). What do the WIMPs do? They provide the force to bind all the particles and do not allow the universe to move away further. Has anyone ever seen these WIMPs with naked eyes? Could anyone prove their existence? The recent scientific studies on consciousness have also found that the hospital patients may benefit from the prayers of strangers, even when they are not aware that someone is praying for them.

According to the researchers, the prayers many be working through magnetic fields or through WIMPs. The old paradigm of observing, theorizing, and predicting doesn't work very well when studying light and consciousness, - especially when it involves the NDEs. It also allows "paradigm cops" to dismiss NDEs as being caused by brain anomalies, even though the cause of NDEs is not relevant to whether the experience is real or not. Nevertheless, recent studies have ruled out brain anomalies. Albert Einstein, the father of the new paradigm, may have old paradigm in mind when he said, "All knowledge of reality starts from experience and ends in it." The new paradigm suggests that we don't merely experience reality; we can create reality within our minds. and if minds can transcend physical bodies and experience clear visions of verified events which could not have been possibly experienced under the old paradigm, then it is time to abandon the old paradigm and focus on the new one. This became even more obvious in December of 2001, when Dr. Pim van Lommel[39] published an article in The Lancet, United Kingdom's highly respected Journal of Medicine, about a study he conducted which showed that 18 percent of clinically dead patients recalled having a NDE. He also documented verified events that were experienced by patients.

Let me return back to NDE. Studies by many scientific researchers showed that 20 and 30% of people, who were resuscitated from a cardiac arrest, experienced NDE, [21] and also that NDE is reproducible in studies in the hospital wards or in the laboratory, where a defibrillator was used. Various other studies have showed the frequency of NDE experience to range between 4 and 28 percent. Popular interest in NDE was sparked by Weiss's book in 1972, called as The Vestibule", followed by Dr. Raymond Moody's [34] book in 1975 called as Life After Life". Also, the International Association for Near-Death Studies (IANDS) was founded in 1977. [1] The experience is typically described as a progression of stages. First, the person may have a sense of peace, followed by a sense of separation from the body and space time dissociation (floating sensation), and seeing his dead body from a height. Some persons feel returning back into their bodies and attempt to do so. Most describe the feeling as very painful. The person then enters into deep darkness through a tunnel (dark energy or dark matter?), and some have described seeing a bright light, like thousands of suns, at the end of the dark tunnel. Finally, the person enters the bright light and interacts with an entity, described as God, Allah, Christ or Jesus, Buddha (Siddhartha) or Guru or simply a universal cosmic force. He/she sometimes merges with this light and then has the mystical feeling of omniscience and all-oneness. [1],[2]However, some people who have survived life-threatening crisis, have reported other extraordinary experiences. Some people have had perceptions of a heavenly or hellish alien landscape or river.

I started a thread bear discussion at BAD Astronomy and Universe Today Forum of USA on 3 rd may 2006 about Human Consciousness and Space Time {please Click and see Web site link [ http://www.bautforum.com/showthread.php/41114-Human-conciousness-and-Space-Time/page4?highlight=Pranab )] and at www.forumastronomydaily.com Or Black hole Forum on 2006 on Definition of Death and Near-Death experience NDE) (which are now occurring with increasing frequency because of improved survival rates due to modern techniques of resuscitation Cardiopulmonary resuscitation (CPR). Many world renowned physicists/people took part in the discussion The content of NDE and the effects on patients seem similar worldwide and across all cultures and time zones. The subjective nature and absence of a frame of reference, has lead to the choice of vocabulary for describing these experiences to be determined by individual, cultural, and religious factors. [3] I shall now summarize the discussions we have had in this article. NDE have reported in many situations, such as, cardiac arrest during myocardial infarction (clinical death), septic shock, shock due to postpartum blood loss (PPH), peri-operative complications, anaphylactic shock, electrocution, diabetic coma, coma resulting from traumatic brain damage, intra-cerebral hemorrhage, cerebral infarction (CVA), attempted suicide, near-drowning or asphyxia, apnea, and use of defibrillators. Such experiences have also been reported by patients with serious but not immediately life-threatening diseases, in those with serious depression, or without clear cause in fully conscious and normal people. Similar NDEs can occur during the terminal phase of illness, or in people who have been intubated with an artificial ventilator in an Intensive Therapy Units (ITU) or intensive care unit (ICU), Respiratory care unit (RCU), and have been called as deathbed visions. Identical experiences to NDEs, called as fear- of death experiences, were also mainly reported after situations in which death seemed unavoidable, such as, serious traffic accidents, mountaineering accidents, or people living in isolation such as in shipwreck situations. There are several scientific theories to explain the origin of NDE.

It has been postulated that the experience is caused by physiological changes in the brain, such as brain cells dying as a result of cerebral anoxia. [4],[5],[6] Other theories encompass a psychological reaction towards approaching death, [5] or a combination of such reaction and anoxia. [7] Such experiences could also be linked to a changing state of consciousness (transcendence), [25] in which perception, cognitive function, emotion, and sense of identity function independently from the normal body, like the waking consciousness.[8] People who had an NDE are usually psychologically healthy, although some show non-pathological signs of dissociation. [9] Such people do not differ from controls with respect to age, sex, ethnic origin, religion, or degree of religious belief. [1] Scientific studies on NDE[2],[3],[5],[10],[11] must always be retrospective in nature, and very much selective with respect to patients, each being given a different questionnaire. In retrospective studies, 5-10 years may elapse between occurrence of such experiences and its investigations, and this often prevents accurate assessment of the physiological and/ or pharmacological factors at that period. The questionnaire may be addressed towards self-image, concern with others, materialism and social issues, religious beliefs and spirituality, and attitude towards death. Participants should answer minimum 34 questions with a five-point scale, [23] indicating whether and to what degree they had changed. There must be a control group, consisting of resuscitated patients who had not reported an NDE. Many results show that medical factors cannot account for occurrence of NDE; although all patients had been clinically dead, most did not have any NDE. Furthermore, seriousness of crisis was not related to occurrence or depth of the experience. It's my personal belief that, if purely physiological factors resulting from cerebral anoxia cause NDE, most of these patients should have had this experience. Patients' medication was also unrelated to frequency of NDE.

In retrospective studies, between 43% [10] and 48% [3] of adults and up to 85% of children [12] who had once a life-threatening illness were estimated to have had an NDE. A random investigation of more than 2000 Germans showed that 43% to had experienced NDE at a mean age of 22 years. [13] Differences in estimates of such frequency may be caused due to varying definitions of the phenomenon, and also due to inadequate research material. [14] Patients' transformational processes after an NDE are very similar, [2],[3],[5],[15],[16],[17],[18]and encompass life-changing insight, heightened intuition, and disappearance of fear of death. Assimilation and acceptance of these changes is thought to take at least several years [19] In another Study [20] , only 12% of patients had a core NDE, and this figure might be an overestimate. When they analyzed their results, they noted that one hospital that participated in the study for nearly 4 years, and from which 137 patients were included, reported a significantly (p = 0·01) lower percentage of NDE (8%), and significantly (p = 0·05) fewer deep experiences. Therefore, possibly patients were selected from other hospitals, who only took part for a few months. In a prospective study[19] 6% of 63 survivors of cardiac arrest reported a core experience, and another 5% had memories with features of an NDE and thus, with their [21] wide definition of the experience, 11% of these patients reported an NDE. Therefore, true frequency of the experience is likely to be about 10%, or 5% if based on number of resuscitations rather than number of resuscitated patients. Patients who survive several CPRs in hospital have a significantly higher chance of NDE. The Worldwide researchers noted that the frequency of NDE was higher in people younger than 60 years than in older people

I would rather like to propose in this article to reassess the theories on the causes and content of NDE. We can medically define clinical brain death of a person as a period of unconsciousness caused by insufficient blood supply to the brain cells, due to various causes, such as, of inadequate blood circulation, breathing, or both. If, in this situation, CPR is not started within 5-10 minutes, irreparable brain damage occurs, and the patient either dies or may proceed to a vegetative state. However, in a brain dead patient, the heart pumping and respiratory functions may remain intact. I have found myself often asking my cardiologist friends of Institute of post graduate medical education and research (IPGMER) Kolkata, West Bengal, India, in such cases "Would we consider the person as alive or dead? Why do we insist on an organ donation or transplant in such conditions? You may say that the individual is in a vegetative state. However, what we need to note is that the person is very much alive, and though in vegetative state, we cannot pronounce them as "dead". Further, though on life support, all the organs of this individual are functioning. There are many examples where such persons in the vegetative state and with life and parenteral nutrient supports, have developed pregnancies through artificial inoculation of sperms, or implantation of a fertilized zygote(IVF) and have even gone ahead to deliver live babies and even revived from the vegetative state after a lock in period. Death can be recorded when the heart stops beating for 5 continuous minutes or with minimum 12 flat lead ECG tracings. Other criteria include stopped respiration for atleast for 8-10 minutes, and the Brain Stem Evoke Potential and auditory Evoke Potential (EP) being totally flat. However, another condition called as "Suspended animation" also exists, where heart beat and respiration stop, but the brain is not dead. Achieving this condition requires a vigorous practice. Many Indian saints and yogis can remain in suspended animation for days together. How can this be possible? But at the moment of death, the individual organ cells or the neuronal cells do not die. Even the cardiac muscle cells, kidney cells and liver cells remain alive. Then-what exactly defines the death of an individual? It is when the "soul" or some energy leaves the body? If yes, immediately after death, there should be some loss, even if in nano grams, in a person's body weight.

A short standardized protocol led interview was done with sufficiently well patients within a few days of CPR resuscitation, and the patients were asked if they recalled anything from the or period of unconsciousness, and about what exactly did they recall, to understand better about the human consciousness.. Researchers in a critical care unit of Government hospital of our state West Bengal can code those experiences according to the weighted core experience index. In this scoring system, [22] depth of NDE may be measured by assigning scores to certain elements in their experiences. Scores between 1 and 5 will then denote superficial NDE, but one can include these events because all patients should undergo transformational changes as well. Scores of 6 or more may denote core experiences, and scores of 10 or greater will be deep experiences. We also should record the date of cardiac arrest, date of interview, sex, age, religion, level of patient education, whether the patient had previously experienced NDE, previously heard of NDE, whether CPR took place inside or outside the hospital, previous history of myocardial infarction, and how many times had the patient been resuscitated during their stay in hospital. We should also estimate duration of circulatory arrest and unconsciousness, and note whether artificial respiration by intubation at ventilator was given.

The patients included are those who have been resuscitated by electrophysiological stimulation procedures. We defined NDE as the reported memory of all impressions during a special state of consciousness, including specific elements, such as, out-of-body experience, pleasant feelings, agony, fighting against death sensation, and seeing and walking through tunnel, a light at end of tunnel. In the next section, we have described some important NDE as recorded by world renowned scientists and who responded in the above stated threads. A cardiologist Prof. Michael Sabom [10] described a near-death experience of his patient, a woman, who was having an unusual surgical procedure for the safe excision and repair of a large basilar artery aneurysm. This woman met all the accepted medical criteria for brain death. The unusual medical procedure involved the induction of hypothermic cardiac arrest, so as to ensure that the aneurysm at the base of the brain would not rupture during the operation. The patient's body temperature was lowered to 60 degrees Fahrenheit, and her heartbeat and breathing ceased, her brain waves were seen as flattened, and the blood was completely drained from her head. Her electroencephalogram (EEG) depicted totally flat readings (indicating no cerebral electrical activity), and auditory evoked potentials (normally elicited by clicks presented through molded earplugs that had been inserted into her ears) ceased (indicating cessation of brainstem functioning). Ordinarily - at regular body temperature, - the brain cannot function without oxygen and glucose supply for more than a few minutes. Lowering the body and brain temperature to below than 60 degrees F, (achieved by chilling the blood in a cardiac bypass machine before returning it to the body and brain) - however, can reduce the cellular metabolism so that the brain can tolerate the complete cerebral blood flow cessation for even up to 45 minutes. The patient later reported that, apparently while under these "brain death" conditions, she had a near-death experience (NDE) in which she was able to observe and hear details of objects and happenings in the operating room with accuracy. She also experienced classic components of the NDE, including a tunnel movement, a light which was equivalent to thousands of suns at the end of that tunnel, and seeing many of her deceased family members, including a distant cousin of his whose death she was even unaware of. Prof. Bruce Greyson MD [9] documented perhaps one of the most compelling examples of a person who had a NDE and observed events, leaving her body, which was even verified by others. The only way that these events could have been observed by the woman was when she in fact was out of her body.

Al Sullivan was a 55 year old truck driver who was undergoing a triple vessel by-pass surgery of coronary artery, when he had a powerful NDE, that included an encounter with his deceased mother and brother-in-law, who told Al Sullivan to go back again to his body, and to tell one of his neighbors, that their son with Non Hodgkin Lymphoma is ultimately going to be fine. Furthermore, during the NDE, Al Sullivan accurately noticed that the surgeon operating on him was flapping his arms in an unusual fashion, with his hands in his armpits. When he came back to his body after the surgery was over, the surgeon was startled that Al Sullivan could accurately describe his own arm flapping, which was his idiosyncratic method of keeping his hands sterile. Addressing the frequent belief that such NDEs can be accounted for as hallucinations, Dr. Greyson [9] noted that if NDEs are indeed hallucinations, then how come they are incredibly accurate and bring up verifiable information? People on drugs such as ketamine, [28] - an anesthetic agent, who have NDEs, see fewer deceased relatives when they travel out of body. This may suggest that people who do see relatives are those who are clear-minded and not hallucinating.

In certain cases, children have seen dead relatives whom they have never even met or not even seen pictures of. This poses the following questions to me: Is accurately seeing the visual images of someone we have never met or seen, actually hallucinating? When assessing the surmounting data of NDEs, Greyson mentioned that the survival hypothesis is the most parsimonious explanation for its growing database. Dr. Kenneth Ring [3] and Dr. Sharon Cooper{33,} completed a two-year study about the NDEs of the blind people. They published their findings in a book entitled "Mindsight," in which they have documented solid evidence of 31 cases in which blind people have reported visually accurate information obtained during an NDE. Perhaps the best example in his study is that of a forty-five year old blind woman by the name of Vicki Umipeg. Vicki was born blind, her optic nerve having been completely destroyed at birth because of an excess of oxygen she received in the incubator. Yet, she appears to have been able to see during her NDE. Her story is a particularly clear instance of how NDEs of the congenitally blind can unfold in precisely the same way as do those of sighted persons.

An anecdotal example of evidence that a person's consciousness leaves and returns to their body during an NDE comes from the research of Dr. Melvin Morse{5,. }. Olga Gearhardt, was a 63 year old woman, had to undergo heart transplant, because of a severe virus that attacked her heart tissue and caused Viral myocardities. Her entire family was at the hospital during the procedure of surgery, except for her son-in-law, who stayed at his home. The transplant was a success, but at exactly 2:15 am, her new heart stopped beating. It took the frantic transplant team three more hours to revive back her. Her family was only told in the morning that her operation was a success, without other details. When they called her son-in-law with the good news, he had his own news to tell. He had already learned about the successful surgery. At exactly 2:15 am, while he was sleeping, he awoke to see his Olga, his mother-in-law, at the foot of his bed. She told him not to worry, that she was going to be alright. She asked him to give her daughter (his wife), a message. He wrote down the message, and the time of day, and then fell asleep. Later on at the hospital, Olga regained consciousness. Her first words were "did you get my message?" She was able to confirm that she left her body during her NDE and was able to travel to her son-in-law to communicate to him the message she wanted to give to her daughter. This anecdotal evidence demonstrates that the NDE is a return to consciousness at the point of death, or when the brain is dying. Dr. Melvin Morse thoroughly researched Olga's testimony and every detail had objective verification, including the scribbled note by the son-in-law. Such testimonies have been similarly documented for hundreds of years.

Fredrick Meyers' classic text entitled "Human Personality and Its Survival After Death" meticulously documents hundreds of such stories. I, Prof Pranab Kumar Bhattacharya MD, have also experienced an NDE when I was sleeping and in the early morning of 10 th April 2009. My 85 year old father, was at his residence (my Parental home is at 7/51 Purbapalli, PO_Sodepur, North 24 Parganas, West Bengal, India), and he was admitted with sudden onset of breathing difficulty at the nearby Panihati State General Hospital (PSG Hospital is a secondary care rural hospital in West Bengal Government health services) by my younger twin brothers Ritwik and Rupak, and Ritwik's wife [who used to look after my parents at per my daily telephonic guidance for last 12 years,]. He was admitted at 2.30 PM on 9 th April, 2009 under the Medical Officer [Physician] through the emergency department for the complaints of sudden breathing difficulty and sudden discomfort in the chest (he complained suddenly he felt his chest became totally empty feeling). My father had a history of Tuberculosis (diagnosed in 1993 treated completely with anti-tuberculosis drug for 18 months), Bronchiactesis because of Tuberculosis, emphysematous large bullas in his middle lobe of left lung and Chronic obstructive pulmonary disease (COPD). His Electrocardiography (ECG) showed normal results. I received the news that he is admitted to to PSG hospital, Sodepur, at night 10-40 PM (at my Mahyamyatala residence of Garia, 54 NSC Bose Road, Kolkata-84 40 Km0 away) from a telephone booth, where I would call up atleast twice a day (morning and night) to enquire about my father's health and give him any medicinal advice. My cell phone was switched off on the day he was admitted as it was a Sunday, and infact I had spoken to him at 13 hours noon. At that time, he did not have any complaints, other than productive cough since three or four days, for which he was taking antibiotic Amoxicillin and Clavelunic acid combination and Deriphyline tablets.

After I received the news on Sunday night at 11 PM, it was practically impossible for me to rush to Sodepur PSG Hospital from Garia, Kolkata, I talked over my cell phone with the on duty visiting Medical Officer and physician, Dr. Rajat Goswami MD (Calcutta University) Medicine, who informed me that my father had developed pneumonia, and necessary antibiotics, by injection, injection Deriphyline, steroid, oxygen and 5% Dextrose Normal Saline drip was being administered. He aslo assured me that there was nothing to worry about. Though I did ask him about a possibility of Acute Myocardial infarction [as he was bed ridden due to blindnedd in both eyes from long standing Glaucoma] or and sudden tension Pnuemothorax (as he had emphysematous bullas in his left middle lobe of lungs) as differential diagnosis, the physician ruled out both of them as he distinctly listened to the S1 and S2 sounds, his pulse was regular, his blood pressure was stable and his condition improved and breathing difficulty diminished with therapy. Also, I had spoken with my father earlier at 13:00 hours when he did not complaint of any chest discomfort and only about the productive cough and slight dyspnea. My father, Late Bholanath Bhattacharya, was a very important personality in Sodepur, as he worked for the refugees from Bangladesh in 1972s.

Due to his social service, his name was mentioned by the Panihati municipality in the history of Sodepur, and his name has been highlighted in the "Sodepur article" in Wikpedia and in many other local newspapers. The attending physician was conscious of this fact. Because of all of this, I went to bed at night very disturbed and worried for my father At 6-40 to 6-42 AM 10 th April, however, out of nowhere, I suddenly heard my father's voice. This again happened at my residence at the Mahamya Apartment, Block B, Mahamyatala, NSC Bose Road, Garia, Kolkata which was 40 KM away from PSG hospital in which my father was admitted. I was in my usual room and till today I remember the voice I heard. He was calling me, and he told me "Bapi (My pet name), wake up, - I am living this world now, and I want to request you to look after your younger twin and other brothers, who are below poverty line along with your own family unit. Do not allow anybody to destroy our family and house. After my departure, there may be a lot of politics played in that house, which may directly involve you and your brothers.". As a person who strongly believed in Science, as a Doctor, as a member of American Association for advancement of Sciences (AAAS) and Nature Network and twenty three other internally reputed Science organizations of the world repute, as a Professor of Pathology -(where I have been a post Graduate and doctoral level teacher, pathologists, immuno pathologists and genetists of different times since 1986), I could not believe my ears and this experience. How would I believe that a person who just had Pneumonia of Lung and under antibiotic and other available care at a primary care hospital, and otherwise okay, could pass away so soon? And also, how could I believe that his soul visited me during the time of his departure? Moreover I never believed in the philosophy of the soul or reincarnation,- though my late mom had a strong belief in God, Re-incarnation, Exo planets, Big Bang theory and the Pan-spermia theory. Thiking that this was just my imagination, I woke up from bed around 7 - 15 AM. Within 5 minutes my wife came from the next room (Where she would sleep with my 10 year old only daughter and my mother in law], and mentioned that there was a telephonic call on the landline from my younger brother Ritwik and his wife, who were outside the PSG hospital ward (they stayed there whole night as per my instructions of not leaving my father alone and watched him from time to time), that our father had expired that morning of 10 thApril morning at 6-40 AM all of a sudden and in their presence. I called up Dr. Rajat Goswami the on duty Physician, and the emergency medical officer, and they mentioned that my father's condition started deteriorating since 5 AM and he expired at 6-40 AM. My old father had never visited me and my family at my late Father -in-law's house at Mahamayatala, Garia, Kolkata, where I was staying since 2006. I still fail to understand how could he find my exact location. We also had to suffer a lot of politics at home after his death, as he had mentioned. Could he really see the future? How could he have caution me about that? I then did a lot of literature search on the scientific background of NDE and the soul.

Many theories have been put forth to explain NDE, and these include the Pro scientific theories (termed as PRO) and the Theological views related with God, and the Soul (termed as CON).Scientific Theories Explaining Near-Death Experiences(1) Dying Brain TheoryPRO: Because NDEs have many common core elements, this shows that they are not spiritual voyages outside of the body, but a function of the dying brain. All brain's cells die in the same way, and that is why all NDEs have the same essential core elements. They are the result of neurotransmitters in the brain shutting down, which can create lovely illusions. (Dr. Susan Blackmore [4]CON: Because NDEs have many common core elements, this suggests that they may be spiritual voyages outside of the body. Also, if the dying brain creates NDE illusions, what is the basic purpose for doing it? If our brains are only like a high-tech super computer-like lump of tissue material which produce our mind and personality, why do they bother to create such illusions only at the time of death? If everything, including the mind and our personality, is about to disintegrate, why would the brain produce a last wonderful Grand Finale vision? Even if NDE elements can be reduced to only a series of brain reactions, this does not negate the idea that NDEs are more than a brain thing. Please Read this article on the errors of the pseudo-skeptics of NDEs-you will enjoy it.(2) Lack of Oxygen TheoryPRO: Neurologist Ernst Rodin offers his theory of cerebral anoxia as a possible cause of NDEs of the dying brain. Such anoxia produces a confusing dream-like state of delusions and hallucinations (Susan Blackmore). [4]CON: Cardiologist Dr. Michael Sabom [10],[24] responded that the NDE involves a clear awareness and a more mystical content, and NDEs have also occurred in people without cerebral anoxia. Pim van Lommel [39] led a study concerning NDEs during cardiac arrest. In their study, all patients had a cardiac arrest, they were declared clinically dead or had unconsciousness that was caused by insufficient blood supply to the brain, and the electroencephalogram (EEG) had only flat readings. In patients, cardiac arrest (ventricular fibrillation) is sometimes induced for testing internal defibrillators. In these patients, the EEG becomes usually flat within 10-15 seconds from the onset of syncope due to the (reversible) total loss of function of the brain. According to the physiologic theory, all patients in their study should have had NDE; however, only 18% actually reported it. [30](3) Right Temporal Lobe TheoryPRO: Neurologist Dr. Michael Persinger argues that instability and activity in the brain's right temporal lobe is responsible for religious experiences of deep meaningfulness, early memories, and out-of-body experiences or quick reviewing of life acts. (see Temporal lobe theory page)CON: Dr. Melvin Morse agrees that the right temporal lobe shows NDE-like activity with Drugs like Ketamine; however, he sees it as the mediating bridge for a spiritual experience, and not statistically reduction as nothing but brain activity (Morse, 1992). Also, the characteristic emotions that result from temporal lobe stimulation are fear, sadness, and loneliness, not the calm and love of a NDE. While scientists may be discovering a mechanism associated with NDEs, this does not mean NDEs are strictly produced by this mechanism. A mechanical function associated with NDEs does not negate the idea that NDEs might be more than a mechanical function.(4) Cortical Dis inhibition TheoryPRO: Susan Blackmore [4] interprets the tunnel and the light as an optical illusion, which can be also created by the effects of anoxia and drugs, creating cortical disinhibition, with the effect of random light spots radiating from the center of a dark internal visual field.CON: Dr. Michael Sabom tested and rejected this brain-only argument. While brain neurology is obviously a part of NDEs, he says, it is not a sufficient explanation because of the verified or veridical aspects found in some NDEs. This aspect suggests the possibility that consciousness can exist outside of the body in dimension less forms. Do Quarks or Neutrinos fermions particles have dimensions?. [10],[22](5) Hallucination TheoryPRO: The psychiatrist Dr. Ronald Siegel interprets NDEs and similar imaginative visions of the afterlife as hallucinations, similar to the effects of psychedelic drugs like Lysergic acid diethylamide (LSD) or anaesthesia. (Hallucination Theory support)CON: Psychologist John Gibbs states, "NDE accounts from varied times and cultures were found to be more orderly, logical, defined and predictable than comparable accounts from drug or illness-induced hallucination. Impressive data from Tart, Moody and Carl Becker also argue for the objective elements of a NDE, including returning with knowledge later verified, and third-party observations of odd death-bed phenomena (such as luminosity or apparitions). Peter Fenwick, a neuropsychiatrist, notes that drug induced hallucinations take place while the subject is conscious and living. During a NDE, the subject is unconscious and near death. While in the state of unconsciousness, the brain cannot create images. Even if they did, the subject must not be able to remember them later. NDEs involve clear, lucid memories. Also, drug induced hallucinations distort reality while NDEs have been described as "hyper-reality."(7) Memory of Birth TheoryPRO: Otto Rank proposed that the birth trauma is behind all neuroses, for all anxiety-producing experiences of separation reactivate the separation from the mother at birth (Brown, 52-53). This theory has been modified to explain the NDE. The Great Astrobiologist cosmologist Prof Carl Sagan FRS proposed that the tunnel and light are a reliving of the infant's descent down the birth canal (Sagan, 353-68). (see Memory of birth page) People want to return back and curl in uterus at time of death.CON: Carl Becker asserts that the infant descending the birth canal has its eyes closed and its brain too undeveloped to allow memories of birth (Becker, 1982). Similarly, Susan Blackmore showed that people who were born by caesarean sections have the tunnel experience and OBEs in equal proportion to those born naturally (Blackmore, 1983). Also, birth is often an unpleasant experience for babies. In contrast, NDEs are often described as extremely pleasurable.(8) Endorphins Theory and Endocrinologists theoryPRO: The brain's naturally produced narcotics, such as the endorphins, have been offered by endocrinologist Daniel Carr to explain why, at the very moment when the body's death would be expected to bring incredible pain and terror, the NDE surprises us with pleasure, calm, and peace.CON: Dr. Melvin Morse responds that patients receiving prescribed narcotics similar to the endorphins, experienced no NDEs (Morse, 1989).(9) Consciousness Survives Bodily Death Theory

PRO: There exists strong circumstantial evidence that consciousness can survive bodily death. While this evidence does not constitute scientific evidence it does make survival after bodily death a possibility that can be upheld in a court of law. The evidence for survival can be found in science, philosophy, history, metaphysics, religion, and anecdotal testimony. Quantum physics makes some scientific theories of the NDE outdated while supporting elements of NDEs. Scientific studies support the possible validity of NDEs elements such as being out of the body, the retention of mental images during brain death, veridical experiences of autoscopic events, the ability to accurately foresee the future, receiving information that leads to new scientific discoveries, people born blind being able to see, groups of people sharing a single experience, unbiased children having similar experiences as adults, causing experiencers to be drastically changed and convinced of survival after death and skepticism. The following is a list of the evidence supporting NDEs as the survival of consciousness. The evidence supports the objectivity of NDEs, and the affirmation of ancient religious concepts is found around the world. Some of the skeptical arguments against the survival theory are often not valid and the burden of proof against survival has shifted to the following:

Quantum physics makes some scientific theories of the NDE outmoded. New developments in quantum physics show that we cannot know phenomena apart from the observer. Arlice Davenport challenges the hallucination theory of NDEs as outmoded because the field theories of physics now suggest new paradigm options available to explain NDEs. Mark Woodhouse argued that the traditional materialism/dualism battle over NDEs may be solved by Einstein's theory of light and energy. Since matter is now seen as a form of energy, an energy body alternative to the material body could explain the NDE. This is supported by Melvin Morse who describes how NDEs are able to realign the charges in the electromagnetic field of the human body so that somehow the brain's wiring is renewed. He reports on patients who have NDEs and who recover from such diseases as pneumonia, cardiac arrest, and cancer (1992, 153-54). Perhaps the brain is like a kind of receiver (such as a television, radio, or cell phone). What is received (i.e., signals, music, voice) is not produced by the receiver, but exists separately as electromagnetic waves that are processed by the receiver to make them visible or audible to the senses.

Quantum physics support elements found in NDEs. Similarities can be found between elements of NDEs and in quantum field concepts of non-locality, universal interconnectedness, a non-material dimension without our time-space relationship, and in the concept of subjectivity. All events are related and influence each other instantaneously and in reciprocity, and only subjectivity remains.

Scientific studies support the out-of-body aspect of NDEs. Pim van Lommel led a study concerning the NDEs of research subjects who had cardiac arrest. The findings of the study suggest that research subjects can experience consciousness, self-identity, cognitive function and memories. One subject Packer had a myocardial infarction while riding a polo pony. A nearby ambulance crew resuscitated him. Packer reported his experience with the comment: "Mate, I tell you there is nothing there". He was obviously not keen to repeat the experience and promptly ensured that the New South Wales ambulance service was equipped with defibrillators. [36],[37]

Science ultimately could not explain me why some people have near-death experiences, while others do not. We cannot say that the current scientific explanations are incorrect. It's just that NDEs are very complex, subjective and emotionally charged. Further, ma­ny aspects of NDEs cannot be tested. We can't run a test to determine if someone actually visited Heaven or the kingdom of death and met God, or purposely take someone to the brink of death and then resuscitate them in a lab to test their out-of-body perception.

Do you believe a soul exists?

Science and medicine seek naturalistic accounts of the observable world. This stance is known as methodological naturalism. Much of the scientific study relating to the soul has involved investigating the soul as an object of human belief, or as a concept that shapes cognition and an understanding of this world rather than as an entity in itself. For much of history, death was often a surprisingly extended process. During this process, the central entity was not the body, but the soul. At the same time, the soul itself could often behave rather like a body. It was a physical thing, which in part obeyed physical laws. [38],[41] Here, there may be two fundamental religious beliefs. One: the soul is an entity, and is potentially vulnerable in the way that other material entities are. Two: the soul does not necessarily leave the body at the moment that the modern science would judge to be that of medical death. In the period before they converted to Christianity, some Roman scientists accepted a kind of spiritual recycling by way of afterlife. [38] When modern scientists speak of the soul outside of this cultural and psychological context, they generally treat soul as a poetic synonym for mind. One of Great scientists and Nobel Laureates in Medicine Francis Crick's book, The Astonishing Hypothesis, for example, has the subtitle, "The scientific search for the soul". Crick held the position that one can learn everything knowable about the human soul by studying the workings of the human brain. Depending on one's belief regarding the relationship between the soul and the mind, then, the findings of neuroscience may be relevant to one's understanding of the soul. Skeptic Robert T. Carroll, suggests that the concept of a non-substantial substance is an oxymoron, and that the scholarship done by philosophers and psychologists based on the assumption of a non-physical entity has not furthered scientific understanding of the working of the mind. Daniel Dennett had championed the idea that the human survival strategy depends heavily on adoption of the intentional stance, a behavioral strategy that predicts the actions of others based on the expectation that they have a mind like one's own (theory of mind). Mirror neurons in brain regions such as Broca's area may facilitate this behavioral strategy. The intentional stance, Dennett suggests, had proven so successful that people tend to apply it to all aspects of human experience, thus leading to animism and to other conceptualizations of soul. In 1907, the US physician Dr Duncan MacDougall made weight measurements of patients as they died. He claimed and registered that there was consistent weight loss of varying amounts at the time of death, precisely 21 grams. [38],[41] MacDougall asserted a universally standard measure for all souls, good or bad, young or old. What weight does the body lose if it was measured three days after death, when putrifications had started, and soul itself would confirm the death? His results have never been reproduced, and are generally regarded either as meaningless or considered to have had little if any scientific merit. Nevertheless, medical science offers compelling evidence that many aspects of NDEs are physiological and psychological in nature.

Scientists have found that the drugs like ketamine and Phencyclidine can create sensations in users that are nearly identical to many NDEs. LSD, [28] pilocarpine, and mescaline can also induce such experiences. [21] These induced experiences can consist of unconsciousness, out-of-body experiences, and perception of light or flashes of recollection from the past. These recollections, however, consist of fragmented and random memories unlike the panoramic life-review that can occur in NDE. Further, transformational processes with changing life-insight and disappearance of fear of death are rarely reported after induced experiences. Thus, induced experiences are not identical to NDE, and so, besides age, an unknown mechanism causes NDE by stimulation of neuro physiological and neuro humoral processes at a sub-cellular level in the brain, in only a few cases during a critical situation such as clinical death. These processes might also determine whether the experience reaches consciousness and can be recollected. In fact, some users think they are actually dying while on the drug. The mechanism behind some of these strange experiences is in the way our brains process sensory information. What we see as "reality" around us is only the sum of all the sensory information our brain is receiving at any given moment. When you look at a computer screen, the light from the screen hits your retinas, and information is sent to the appropriate areas of the brain to interpret the light patterns into something meaningful,-in this case, the words you are currently reading. An even more complex system of nerves and muscle fibers allows your brain to know, where your body is in relation to the space around it. Close your eyes and raise your right hand until it is level with the top of your head. How do you know where your hand is without looking at it? This sensory system allows you to know where your hand is even when your eyes are closed. Now imagine that all your senses are malfunctioning. Instead of real sensory input from the world around you, your brain is receiving all faulty information, possibly because of drugs, or some form of trauma that is causing your brain to shut down. What you perceive as a real experience is actually your brain trying to interpret this information. Some have theorized that "neural noise," or an overload of information sent to the brain's visual cortex, creates an image of a bright light that gradually grows larger. The brain may interpret this as moving down a dark tunnel. The body's spatial sense is prone to malfunctions during a near-death experience as well.

Again, your brain interprets faulty information about where the body is in relation to the space around it. The result is the sensation of leaving the body and flying around the room. Combined with other effects of trauma, the peaceful, calm sensation felt during NDEs may be a coping mechanism triggered by increased levels of endorphins produced due to oxygen deprivation in the brain (a symptom in many near-death situations), and this leads to the overall experience of floating into space, of looking down at your own body, and then leaving to float down a tunnel. Many people experience a strange sense of detachment and a lack of emotional response during traumatic events (whether or not they were related to a near-death experience). This is the same effect. NDEs that include visits to Heaven or meetings with God could involve a combination of several factors. Faulty sensory input, oxygen deprivation and endorphin-induced euphoria may create a surreal, though realistic, experience. When the subject recalls the encounter later, it has passed through the filter of his conscious mind. Bizarre experiences that seem unexplainable become spirit beings, other dimensions and conversations with God. The experiences of people whose out-of-body adventures allow them to see and hear events that their unconscious body shouldn't be able to perceive are more difficult to explain. However, it is plausible that unconscious people can still register sensory cues and prior knowledge and incorporate them into their NDE.

Out of Body Experience may probably be defined as sleep paralysis also, and it happens during the dissociated rapid-eye-movement (REM) sleep state. Cheyne and his colleagues reported 17 such cases of autoscopic Out of Body experiences associated with "sleep paralysis" in their Journal "the Lancet", in which the individuals viewed themselves as lying on the bed, generally from a location above the bed. However by use of positron emission tomography (PET) scanning of Brain, Maquet and colleagues noted a significant negative correlation between the regional cerebral blood flow (rCBF) and REM sleep in a large area of the dorso-lateral, prefrontal cortex and the parietal cortex, temporal cortex, and a significant positive correlation between rCBF and REM sleep in the limbic-system structures implicated in the formation and consolidation of memories. In dissociated REM sleep states, activation of such limbic structures during inhibition of the neo-cortex may lead to an iric recollection of images concerning the individual's sleeping environment. Likewise, in near-death experiences, out-of-body visions, and possibly other phenomena, such as passing through a dark tunnel , flashes light of a thousand suns, Godly structures, recollection from the past events, and even quick life reviews of one works in this planet, reported by many some patients of authors previous work, may represent a dis-inhibition of limbic system structures of brain due to hypoxic suppression of the neo-cortex, rather than any paranormal phenomena or any false memories.

Paranormal phenomena such as ghosts, or Hindu religious belief, and events such as possible reincarnation in human or other forms, as per his/her works, may be explained through distortion over the ages of any near-death experiences. Bruno Bettelheim [35],[37] drew the attention of people to the importance of myth, legend, and fairytales, as a roadmap to overcoming adversity on the pathway to maturity. Near-death experiences may prove to be a fountain head for these devices and, as such, be central to spirituality rather than stemming from it. The other element that does not attract comment is the over whelming positive nature of the near-death experience. This positivity could represent the optimism for the presence of human spirit and soul, or maybe it ensures that the experience is totally subjective one to recall and recount. It may also underpin one of the most quoted biblical phrases from Psalm 23: "Yea, though I walk through the kingdom of the valley of death, I will fear no evil".

However after an NDE, majority NDEers are however absolutely certain that there is "life after death". [32],[33],[34],[35] That is however good in one sense. Other researches and even I have observed a rather positive consequence: some NDE ers mourn less because they know that there is life after death. [2],[32],[33],[34]

Acknowledgements and Copy Right Statement

The author deeply acknowledges with his heartfelt greatness for contributions by Miss Upasana Bhattacharya,- a student and the only daughter of Prof. Pranab Kumar Bhattacharya, Mr Rupak Bhattacharya, Mr. Ritwik Bhattacharya, Miss Rupsa Bhattacharya, Mr. Soumyak Bhattacharya of residence at 7/51Purbapalli, PO-Sodepur, 24 Parganas (north), Kol-110, Ps Khardaha, West Bengal, India, and Mrs. Dalia Mukherjee, BA(hons) cal; Miss Oaidrila Mukherjee- BA(Hons) Student and Mr. Debasis Mukherjee Bsc(cal) of Swamiji Nagar, South Habra, 24 Parganas (north), W.B, India. This article has been dedicated to the author's diseased parents- late Bholanath Bhattacharya [whose name is reflected in the history section in the article "Sodepur" of Wikipedia, In "Bangla Darpan Newspaper of West Bengal" and in information and references provided by the local Panihati municipality, Sodepur] and late Mrs. Bani Bhattacharya, as a tribute and the copy Right of this article strictly belongs to Professor Pranab kumar Bhattacharya MD(cal) and his first degree blood relatives only, under Copy Right Rules of intellectual property Right [IPR], under section 3D/107/ 1021 a b ; RDF/ SPARC -2006 and Protection of Intellectual Property laws [PIP] of United States of America-2012. The Quantum particles views about human consciousness, NDE and Soul in this article belong only to the authors.Do not try to infringe for your own safety from Plagiarism

Jansen K. Neuroscience, ketamine and the near-death experience: The role of glutamate and the NMDA-receptor. In: Bailey LW,Yates J, eds. The near-death experience: A reader. New York and London: Routledge, 1996: 265-82.

2]You can also see the Recent Publication one day ago in one of Top world journal " Proceedings of the National Academy of sciences United States of America ( PNAS) on Near Death Experences Published online before print August 12, 2013, doi:10.1073/pnas.1308285110 Article Titlle is "Surge of neuro physiological coherence and connectivity in the dying brain" by following authors